Phrenic nerve stimulation for central ventilatory failure with bipolar and four-pole electrode systems.

A multi-channel phrenic nerve stimulator developed in Tampere has been implanted into seven patients with C2-tetraplegia and into three patients with central sleep apneas. Six bipolar cuff electrodes were implanted bilaterally into the neck. Two four-pole cuff and 14 four-pole noncuff electrodes were used in seven patients and to replace one bipolar electrode. Four-pole electrodes were implanted within the thorax. Seven patients achieved total independence from conventional ventilators within 4 months of implantation, and one for 18 hours each day. Two patients died 12 days and 3 months after implantation and two patients after having achieved independence from mechanical ventilators from causes unrelated to the stimulators. Reoperations were necessary because of dislocation of receivers, electrodes, electrode lesions, nerve injuries, and technical failures in seven patients. Most of the problems appeared in two patients with obesity and in three patients with very thin phrenic nerves. Single unit prototypes failed technically more frequently than units of prototype serial fabrication. New electrode design, progress in the manufacture of receivers, and improved implantation technique should help to diminish failures in future.